moving a word to an array of bytes

[aw27]

If you return from the main thread, does the process exit?

If there is more than 1 thread it will not.

[mineiro]

hello sir nickc86;
yes, you're thinking right, you can access members of that array by the way you show.
But you can create a structure too, so you dont need calculate position member based on address because assembler can do that job to you. This is good because on a future you can insert or also change members place without need to go to code and change all member array reference by calculating.

[nickc86]

This is for a project at university. I'll be copying this array using movsb, so I don't know that creating a structure for this is the way to go. This array will be going in to another block of memory for later processing. I will have something that looks like this

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packetsize equ 8
numpackets equ 20
packet byte packetsize dup (?)
queue byte numpackets*packetsize dup (?)

And I'll want to do things like

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mov eax, OFFSET queue
;get the third byte of the second packet
add eax, packetsize
mov bl, byte ptr [eax + 2]


Or doing this

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;copy the 3rd packet
mov eax, 3
imul eax, packetsize
mov esi, OFFSET queue
add esi, eax
mov ecx, packetsize
mov edi, OFFSET packet
cld
rep movsb


Would I be going about this in the correct manner?

[mineiro]

yes, you can go that way.

But I want to access those 8 bytes in the following order:
byte byte byte alignbyte word word

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my_structure struct
bone db ?
btwo db ?
bthree db ?
pad db ?
wone dw ?
wtwo dw ?
my_structure ends

.data
;...
.code
  mov eax, OFFSET queue
  assume eax:ptr my_structure
  mov [eax].wone,5645
  mov cx,[eax].wone
  assume eax:nothing
  add eax, sizeof my_structure

  assume eax:ptr my_struct_inside_struct
  ...


--edited--
showing other examples:
  add eax,sizeof my_structure*packetsize+numpackets
  add eax, sizeof my_structure*sizeof other_struct*packetsize/sizeof otherstruct

[mineiro]

hello sir jj2007;

On ms-dos an exitprocess can be just 'ret'. On windows too

On Windows, ret will trigger RtlExitUserThread - not the best option. But it will indeed work most of the time.

See also Raymond Chen's If you return from the main thread, does the process exit?

On ms-dos an exitprocess can be just 'ret'. On windows too, but on linux not, but this is a bad pratice.

int 20h to .com, int 21h to .exe, int 80h on linux 32, syscall on linux 64, ExitProcess on windows 32 and 64...

[nidud]

deleted

[RuiLoureiro]

Helllo Nidud,  :t
  :icon14: